The invention relates to a quick fastener for connecting a first part and a second part for connecting a mixer tube and a connector part of an extruder unit. The first part has a conical threaded base member with an external thread running along the conical threaded member. The second part has a conical threaded base member with an internal thread running in the conical threaded base member.
The bayonet coupling is known as a quick-acting fastening or closure, wherein one part is inserted with a tappet into another part having a corresponding receptacle, and by rotation is fastened to the first part. DE 198 38 560 discloses a rotary quick-acting closure for interconnecting a plurality of structural parts with each other, whereby the holding part has clamping projections, which engage a second structural part by rotating the holding part. This known quick-acting closure can be quickly closed and can translate only limited high forces.
Particularly in an extrusion unit for paste-like masses high forces occur at the interface of connecting part and a mixer tube, said forces having to be sustained by the connection. Cylindrical round threads are well-known for translation of these high forces over the connection. These are expensive in this application because several rotations are required for establishing the connection between the parts.
U.S. Pat. No. 4,798,195 A discloses a closure that has a connection associated with a conical thread with progressively decreasing diameter in the direction of the opening. The container can be closed with minimum rotation by virtue of the closure cap configured to be complementary to the connection. The drawback in this solution is that manufacturing the thread in an injection molding process is very expensive, in terms of time and cost, because of the completely necessary unwinding of the thread.
U.S. Pat. No. 4,699,285 A discloses a closure for bottles, wherein the thread are conically inclined on the bottle and the zone of the thread has a constant wall thickness and uniform flank height. The drawback of this solution is using this connection that is capable of sustaining only conditionally high forces such as those that occur in connections in extrusion units.